1. Field of the Invention
The present invention relates to PCL (passive coherent location) applications, and more particularly, to a system and method for wideband pre-detection signal processing for PCL applications.
2. Discussion of the Related Art
Radar systems detect the presence of a target of interest and provide information about that target. Conventional radar systems include pulsed radar and continuous wave radar. In pulsed radar, the measure of target distance is determined by the measurement of the time elapsed from the transmission of an electromagnetic energy pulse to the reception of its reflected energy. In continuous wave radar, a continuous wave is transmitted. The target distance is determined through the measurement of the frequency shift between the transmitted signal and the received reflected signal.
Conventional radar systems transmit electromagnetic energy. A portion of the transmitted electromagnetic energy is reflected off a target of interest and scattered in the space. The radar system receives the reflected energy and extracts the information about the target of interest by correlating the received reflected energy with replicas of the transmitted energy.
Passive radar systems, in contrast to conventional radar systems, exploit electromagnetic energy transmitted from uncontrolled illuminators, such as commercial broadcast FM radio signals and television broadcast signals. Passive radar systems receive reflected signals, which are the signals transmitted from uncontrolled illuminators and reflected off the target of interest, and direct path signals from the uncontrolled illuminators. The passive radar systems extract the information about the target of interest by correlating the received reflected signals with the received direct path signals used as a reference signal.
PCL (passive coherent location) system is a passive surveillance system including multi-static wide area moving target surveillance sensors. PCL technology provides detection capability without transmitting energy. In a PCL system, tracking accuracy and resolution are important.
Accordingly, the present invention is directed to a PCL application and method for signal processing for a PCL application.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, A method for wideband pre-detection signal processing in PCL applications includes a first reference signal and a first target signal, filtering the first reference signal with respect to the first target signal using a filter to form a first output reference signal, combining the first output reference signal with the first target signal to form a first output target signal, receiving a second reference signal and a second target signal, updating the filter with respect to a change between the first target signal and the second target signal, filtering the second reference signal using the updated filter to form a second output reference signal, and combining the second output reference signal with the second target signal to form a second output target signal.
In another aspect of the present invention, a method for wideband pre-detection signal processing in PCL applications includes receiving a target signal and a reference signal, forming a plurality of target beams from the target signal, forming a plurality of lag products for each of the plurality of target beams, decimating each of the plurality of lag products for each of the plurality of target beams, forming a plurality of lag products for the reference signal, and decimating each of the plurality of lag products for the reference signal.
In another aspect of the present invention, a method for wideband pre-detection signal processing for Passive Coherent Location (PCL) applications includes receiving an input signal, estimating a reference signal and a target signal from the input signal, reducing a portion of the reference signal in the target signal, wherein the reference signal is adaptively filtered with respect to the target signal and combined with the target signal to form an output target signal, forming a plurality of target beams for the output target signal, forming a plurality of decimated lag products for each of the plurality of target beams, and forming a plurality of decimated lag products for the reference signal.
In another aspect of the present invention, a method for wideband pre-detection signal processing in PCL applications includes receiving an input signal, extracting a target signal and a reference signal from the input signal, implementing a transformation operation on the target signal and the reference signal, compensating the transformed target signal and the transformed reference signal for channel distortion, reducing a portion of the compensated reference signal in the compensated target signal, wherein the compensated reference signal is adaptively filtered with respect to the compensated target signal and combined with the compensated target signal to form an output target signal, demodulating and forming complex-valued representations of the compensated reference signal and the output target signal, implementing an inverse transformation on the compensated reference signal and the output target signal, forming a plurality of target beams for the output target signal, forming a plurality of decimated lag products for each of the plurality of target beams, forming a plurality of decimated lag products for the compensated reference signal, estimating a cross ambiguity function for the each of plurality of target beams using the plurality of decimated lag products for each of the plurality of target beams, and estimating an auto ambiguity function for the reference signal using the plurality of decimated lag products for the reference signal.
In another aspect of the present invention, a system for pre-detection signal processing for wideband in PCL applications including a first functional element includes a first sub-element for receiving a first reference signal and a first target signal, and a second reference signal and a second target signal in series, a second sub-element for filtering the first reference signal with respect to the first target signal using a filter to form a first output reference signal, a third sub-element for combining the first output reference signal with the first target signal to from a first output target signal, and a forth sub-element for updating the second element with respect to a change between the first target signal and the second target signal.
In another aspect of the present invention, a system for pre-detection signal processing for wideband in PCL applications including a first functional element includes a first sub-element for receiving a target signal and a reference signal, a second sub-element for forming a plurality of target beams for the target signal, a third sub-element for forming a plurality of lag products for each of the plurality of target beams, a fourth sub-element for decimating each of the plurality of lag products for each of the plurality of target beams, a fifth sub-element for forming a plurality of lag products for the reference signal, and a sixth sub-element for decimating each of the plurality of lag products for the reference signal.
In another aspect of the present invention, a system for pre-detection signal processing for wideband in PCL applications includes first functional element for receiving an input signal including a target signal and a reference signal, a second functional element for implementing a transformation operation on the target signal and the reference signal, a third functional element for compensating the transformed target signal and the transformed reference signal for channel distortion, a fourth functional element for reducing a portion of the compensated reference signal in the compensated target signal, wherein the compensated reference signal is adaptively filtered with respect to the compensated target signal and combined with the compensated target signal to form an output target signal, a fifth functional element for demodulating and forming complex-valued representations of the compensated reference signal and the output target signal, a sixth functional element for forming a plurality of target beams for the output target signal, and a seventh functional element for forming a plurality of decimated lag products for each of the plurality of target beams and a plurality of decimated lag products for the reference signal.
In another aspect of the present invention, a system for pre-detection signal processing for wideband in PCL applications includes a first functional element for receiving an input signal, a second functional element for implementing a transformation operation on the input signal, a third functional element for compensating the transformed input signal for channel distortion, a fourth functional element for demodulating and forming complex-valued representations of the compensated input signal, a fifth functional element for estimating a target signal and a reference signal from the input signal received from the fourth functional element, a sixth functional element for reducing a portion of the reference signal in the target signal, wherein the reference signal is adaptively filtered with respect to the target signal and combined with the target signal to form an output target signal, a seventh functional element for forming a plurality of target beams for the output target signal, and an eighth functional element for forming a plurality of decimated lag products for each of the plurality of target beams and a plurality of decimated lag products for the reference signal.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.